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                    option选项
            
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        <li class="chapter " data-level="1.12.7" data-path="../elements/video.html">
            
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                    video,audio音视频
            
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                                <section class="normal markdown-section">
                                
                                <h1 id="&#x4E25;&#x683C;&#x6A21;&#x5F0F;">&#x4E25;&#x683C;&#x6A21;&#x5F0F;</h1>
<p>&#x9664;&#x4E86;&#x6B63;&#x5E38;&#x7684;&#x8FD0;&#x884C;&#x6A21;&#x5F0F;&#xFF0C;JavaScript &#x8FD8;&#x6709;&#x7B2C;&#x4E8C;&#x79CD;&#x8FD0;&#x884C;&#x6A21;&#x5F0F;&#xFF1A;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF08;strict mode&#xFF09;&#x3002;&#x987E;&#x540D;&#x601D;&#x4E49;&#xFF0C;&#x8FD9;&#x79CD;&#x6A21;&#x5F0F;&#x91C7;&#x7528;&#x66F4;&#x52A0;&#x4E25;&#x683C;&#x7684; JavaScript &#x8BED;&#x6CD5;&#x3002;</p>
<p>&#x540C;&#x6837;&#x7684;&#x4EE3;&#x7801;&#xFF0C;&#x5728;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x548C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E2D;&#xFF0C;&#x53EF;&#x80FD;&#x4F1A;&#x6709;&#x4E0D;&#x4E00;&#x6837;&#x7684;&#x8FD0;&#x884C;&#x7ED3;&#x679C;&#x3002;&#x4E00;&#x4E9B;&#x5728;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#x53EF;&#x4EE5;&#x8FD0;&#x884C;&#x7684;&#x8BED;&#x53E5;&#xFF0C;&#x5728;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#x5C06;&#x4E0D;&#x80FD;&#x8FD0;&#x884C;&#x3002;</p>
<h2 id="&#x8BBE;&#x8BA1;&#x76EE;&#x7684;">&#x8BBE;&#x8BA1;&#x76EE;&#x7684;</h2>
<p>&#x65E9;&#x671F;&#x7684; JavaScript &#x8BED;&#x8A00;&#x6709;&#x5F88;&#x591A;&#x8BBE;&#x8BA1;&#x4E0D;&#x5408;&#x7406;&#x7684;&#x5730;&#x65B9;&#xFF0C;&#x4F46;&#x662F;&#x4E3A;&#x4E86;&#x517C;&#x5BB9;&#x4EE5;&#x524D;&#x7684;&#x4EE3;&#x7801;&#xFF0C;&#x53C8;&#x4E0D;&#x80FD;&#x6539;&#x53D8;&#x8001;&#x7684;&#x8BED;&#x6CD5;&#xFF0C;&#x53EA;&#x80FD;&#x4E0D;&#x65AD;&#x6DFB;&#x52A0;&#x65B0;&#x7684;&#x8BED;&#x6CD5;&#xFF0C;&#x5F15;&#x5BFC;&#x7A0B;&#x5E8F;&#x5458;&#x4F7F;&#x7528;&#x65B0;&#x8BED;&#x6CD5;&#x3002;</p>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x662F;&#x4ECE; ES5 &#x8FDB;&#x5165;&#x6807;&#x51C6;&#x7684;&#xFF0C;&#x4E3B;&#x8981;&#x76EE;&#x7684;&#x6709;&#x4EE5;&#x4E0B;&#x51E0;&#x4E2A;&#x3002;</p>
<ul>
<li>&#x660E;&#x786E;&#x7981;&#x6B62;&#x4E00;&#x4E9B;&#x4E0D;&#x5408;&#x7406;&#x3001;&#x4E0D;&#x4E25;&#x8C28;&#x7684;&#x8BED;&#x6CD5;&#xFF0C;&#x51CF;&#x5C11; JavaScript &#x8BED;&#x8A00;&#x7684;&#x4E00;&#x4E9B;&#x602A;&#x5F02;&#x884C;&#x4E3A;&#x3002;</li>
<li>&#x589E;&#x52A0;&#x66F4;&#x591A;&#x62A5;&#x9519;&#x7684;&#x573A;&#x5408;&#xFF0C;&#x6D88;&#x9664;&#x4EE3;&#x7801;&#x8FD0;&#x884C;&#x7684;&#x4E00;&#x4E9B;&#x4E0D;&#x5B89;&#x5168;&#x4E4B;&#x5904;&#xFF0C;&#x4FDD;&#x8BC1;&#x4EE3;&#x7801;&#x8FD0;&#x884C;&#x7684;&#x5B89;&#x5168;&#x3002;</li>
<li>&#x63D0;&#x9AD8;&#x7F16;&#x8BD1;&#x5668;&#x6548;&#x7387;&#xFF0C;&#x589E;&#x52A0;&#x8FD0;&#x884C;&#x901F;&#x5EA6;&#x3002;</li>
<li>&#x4E3A;&#x672A;&#x6765;&#x65B0;&#x7248;&#x672C;&#x7684; JavaScript &#x8BED;&#x6CD5;&#x505A;&#x597D;&#x94FA;&#x57AB;&#x3002;</li>
</ul>
<p>&#x603B;&#x4E4B;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4F53;&#x73B0;&#x4E86; JavaScript &#x66F4;&#x5408;&#x7406;&#x3001;&#x66F4;&#x5B89;&#x5168;&#x3001;&#x66F4;&#x4E25;&#x8C28;&#x7684;&#x53D1;&#x5C55;&#x65B9;&#x5411;&#x3002;</p>
<h2 id="&#x542F;&#x7528;&#x65B9;&#x6CD5;">&#x542F;&#x7528;&#x65B9;&#x6CD5;</h2>
<p>&#x8FDB;&#x5165;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7684;&#x6807;&#x5FD7;&#xFF0C;&#x662F;&#x4E00;&#x884C;&#x5B57;&#x7B26;&#x4E32;<code>use strict</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
</code></pre>
<p>&#x8001;&#x7248;&#x672C;&#x7684;&#x5F15;&#x64CE;&#x4F1A;&#x628A;&#x5B83;&#x5F53;&#x4F5C;&#x4E00;&#x884C;&#x666E;&#x901A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x52A0;&#x4EE5;&#x5FFD;&#x7565;&#x3002;&#x65B0;&#x7248;&#x672C;&#x7684;&#x5F15;&#x64CE;&#x5C31;&#x4F1A;&#x8FDB;&#x5165;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x3002;</p>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x53EF;&#x4EE5;&#x7528;&#x4E8E;&#x6574;&#x4E2A;&#x811A;&#x672C;&#xFF0C;&#x4E5F;&#x53EF;&#x4EE5;&#x53EA;&#x7528;&#x4E8E;&#x5355;&#x4E2A;&#x51FD;&#x6570;&#x3002;</p>
<p><strong>&#xFF08;1&#xFF09; &#x6574;&#x4E2A;&#x811A;&#x672C;&#x6587;&#x4EF6;</strong></p>
<p><code>use strict</code>&#x653E;&#x5728;&#x811A;&#x672C;&#x6587;&#x4EF6;&#x7684;&#x7B2C;&#x4E00;&#x884C;&#xFF0C;&#x6574;&#x4E2A;&#x811A;&#x672C;&#x90FD;&#x5C06;&#x4EE5;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x8FD0;&#x884C;&#x3002;&#x5982;&#x679C;&#x8FD9;&#x884C;&#x8BED;&#x53E5;&#x4E0D;&#x5728;&#x7B2C;&#x4E00;&#x884C;&#x5C31;&#x65E0;&#x6548;&#xFF0C;&#x6574;&#x4E2A;&#x811A;&#x672C;&#x4F1A;&#x4EE5;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x8FD0;&#x884C;&#x3002;(&#x4E25;&#x683C;&#x5730;&#x8BF4;&#xFF0C;&#x53EA;&#x8981;&#x524D;&#x9762;&#x4E0D;&#x662F;&#x4EA7;&#x751F;&#x5B9E;&#x9645;&#x8FD0;&#x884C;&#x7ED3;&#x679C;&#x7684;&#x8BED;&#x53E5;&#xFF0C;<code>use strict</code>&#x53EF;&#x4EE5;&#x4E0D;&#x5728;&#x7B2C;&#x4E00;&#x884C;&#xFF0C;&#x6BD4;&#x5982;&#x76F4;&#x63A5;&#x8DDF;&#x5728;&#x4E00;&#x4E2A;&#x7A7A;&#x7684;&#x5206;&#x53F7;&#x540E;&#x9762;&#xFF0C;&#x6216;&#x8005;&#x8DDF;&#x5728;&#x6CE8;&#x91CA;&#x540E;&#x9762;&#x3002;)</p>
<pre><code class="lang-html"><span class="hljs-tag">&lt;<span class="hljs-name">script</span>&gt;</span><span class="javascript"><span class="hljs-meta">
  &apos;use strict&apos;</span>;
  <span class="hljs-built_in">console</span>.log(<span class="hljs-string">&apos;&#x8FD9;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&apos;</span>);
</span><span class="hljs-tag">&lt;/<span class="hljs-name">script</span>&gt;</span>

<span class="hljs-tag">&lt;<span class="hljs-name">script</span>&gt;</span><span class="javascript">
  <span class="hljs-built_in">console</span>.log(<span class="hljs-string">&apos;&#x8FD9;&#x662F;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&apos;</span>);
</span><span class="hljs-tag">&lt;/<span class="hljs-name">script</span>&gt;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x4E00;&#x4E2A;&#x7F51;&#x9875;&#x6587;&#x4EF6;&#x4F9D;&#x6B21;&#x6709;&#x4E24;&#x6BB5; JavaScript &#x4EE3;&#x7801;&#x3002;&#x524D;&#x4E00;&#x4E2A;<code>&lt;script&gt;</code>&#x6807;&#x7B7E;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x540E;&#x4E00;&#x4E2A;&#x4E0D;&#x662F;&#x3002;</p>
<p>&#x5982;&#x679C;<code>use strict</code>&#x5199;&#x6210;&#x4E0B;&#x9762;&#x8FD9;&#x6837;&#xFF0C;&#x5219;&#x4E0D;&#x8D77;&#x4F5C;&#x7528;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x5FC5;&#x987B;&#x4ECE;&#x4EE3;&#x7801;&#x4E00;&#x5F00;&#x59CB;&#x5C31;&#x751F;&#x6548;&#x3002;</p>
<pre><code class="lang-html"><span class="hljs-tag">&lt;<span class="hljs-name">script</span>&gt;</span><span class="javascript">
  <span class="hljs-built_in">console</span>.log(<span class="hljs-string">&apos;&#x8FD9;&#x662F;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&apos;</span>);
  <span class="hljs-string">&apos;use strict&apos;</span>;
</span><span class="hljs-tag">&lt;/<span class="hljs-name">script</span>&gt;</span>
</code></pre>
<p><strong>&#xFF08;2&#xFF09;&#x5355;&#x4E2A;&#x51FD;&#x6570;</strong></p>
<p><code>use strict</code>&#x653E;&#x5728;&#x51FD;&#x6570;&#x4F53;&#x7684;&#x7B2C;&#x4E00;&#x884C;&#xFF0C;&#x5219;&#x6574;&#x4E2A;&#x51FD;&#x6570;&#x4EE5;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x8FD0;&#x884C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">strict</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;&#x8FD9;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&apos;</span>;
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">strict2</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;&#x8FD9;&#x4E5F;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&apos;</span>;
  }
  <span class="hljs-keyword">return</span> f();
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">notStrict</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;&#x8FD9;&#x662F;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&apos;</span>;
}
</code></pre>
<p>&#x6709;&#x65F6;&#xFF0C;&#x9700;&#x8981;&#x628A;&#x4E0D;&#x540C;&#x7684;&#x811A;&#x672C;&#x5408;&#x5E76;&#x5728;&#x4E00;&#x4E2A;&#x6587;&#x4EF6;&#x91CC;&#x9762;&#x3002;&#x5982;&#x679C;&#x4E00;&#x4E2A;&#x811A;&#x672C;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x53E6;&#x4E00;&#x4E2A;&#x811A;&#x672C;&#x4E0D;&#x662F;&#xFF0C;&#x5B83;&#x4EEC;&#x7684;&#x5408;&#x5E76;&#x5C31;&#x53EF;&#x80FD;&#x51FA;&#x9519;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7684;&#x811A;&#x672C;&#x5728;&#x524D;&#xFF0C;&#x5219;&#x5408;&#x5E76;&#x540E;&#x7684;&#x811A;&#x672C;&#x90FD;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF1B;&#x5982;&#x679C;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x7684;&#x811A;&#x672C;&#x5728;&#x524D;&#xFF0C;&#x5219;&#x5408;&#x5E76;&#x540E;&#x7684;&#x811A;&#x672C;&#x90FD;&#x662F;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x3002;&#x8FD9;&#x4E24;&#x79CD;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x5408;&#x5E76;&#x540E;&#x7684;&#x7ED3;&#x679C;&#x90FD;&#x662F;&#x4E0D;&#x6B63;&#x786E;&#x7684;&#x3002;&#x8FD9;&#x65F6;&#x53EF;&#x4EE5;&#x8003;&#x8651;&#x628A;&#x6574;&#x4E2A;&#x811A;&#x672C;&#x6587;&#x4EF6;&#x653E;&#x5728;&#x4E00;&#x4E2A;&#x7ACB;&#x5373;&#x6267;&#x884C;&#x7684;&#x533F;&#x540D;&#x51FD;&#x6570;&#x4E4B;&#x4E2D;&#x3002;</p>
<pre><code class="lang-javascript">(<span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-comment">// some code here</span>
})();
</code></pre>
<h2 id="&#x663E;&#x5F0F;&#x62A5;&#x9519;">&#x663E;&#x5F0F;&#x62A5;&#x9519;</h2>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4F7F;&#x5F97; JavaScript &#x7684;&#x8BED;&#x6CD5;&#x53D8;&#x5F97;&#x66F4;&#x4E25;&#x683C;&#xFF0C;&#x66F4;&#x591A;&#x7684;&#x64CD;&#x4F5C;&#x4F1A;&#x663E;&#x5F0F;&#x62A5;&#x9519;&#x3002;&#x5176;&#x4E2D;&#x6709;&#x4E9B;&#x64CD;&#x4F5C;&#xFF0C;&#x5728;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#x53EA;&#x4F1A;&#x9ED8;&#x9ED8;&#x5730;&#x5931;&#x8D25;&#xFF0C;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<h3 id="&#x53EA;&#x8BFB;&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;">&#x53EA;&#x8BFB;&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x8BBE;&#x7F6E;&#x5B57;&#x7B26;&#x4E32;&#x7684;<code>length</code>&#x5C5E;&#x6027;&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-string">&apos;abc&apos;</span>.length = <span class="hljs-number">5</span>;
<span class="hljs-comment">// TypeError: Cannot assign to read only property &apos;length&apos; of string &apos;abc&apos;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x62A5;&#x9519;&#xFF0C;&#x56E0;&#x4E3A;<code>length</code>&#x662F;&#x53EA;&#x8BFB;&#x5C5E;&#x6027;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#x4E0D;&#x53EF;&#x5199;&#x3002;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x6539;&#x53D8;<code>length</code>&#x5C5E;&#x6027;&#x662F;&#x65E0;&#x6548;&#x7684;&#xFF0C;&#x4F46;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5BF9;&#x53EA;&#x8BFB;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#xFF0C;&#x6216;&#x8005;&#x5220;&#x9664;&#x4E0D;&#x53EF;&#x914D;&#x7F6E;&#xFF08;non-configurable&#xFF09;&#x5C5E;&#x6027;&#x90FD;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// &#x5BF9;&#x53EA;&#x8BFB;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#x4F1A;&#x62A5;&#x9519;</span>
<span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;a&apos;</span>, {
  value: <span class="hljs-number">37</span>,
  writable: <span class="hljs-literal">false</span>
});
obj.a = <span class="hljs-number">123</span>;
<span class="hljs-comment">// TypeError: Cannot assign to read only property &apos;a&apos; of object #&lt;Object&gt;</span>

<span class="hljs-comment">// &#x5220;&#x9664;&#x4E0D;&#x53EF;&#x914D;&#x7F6E;&#x7684;&#x5C5E;&#x6027;&#x4F1A;&#x62A5;&#x9519;</span>
<span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">1</span>,
  configurable: <span class="hljs-literal">false</span>
});
<span class="hljs-keyword">delete</span> obj.p
<span class="hljs-comment">// TypeError: Cannot delete property &apos;p&apos; of #&lt;Object&gt;</span>
</code></pre>
<h3 id="&#x53EA;&#x8BBE;&#x7F6E;&#x4E86;&#x53D6;&#x503C;&#x5668;&#x7684;&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;">&#x53EA;&#x8BBE;&#x7F6E;&#x4E86;&#x53D6;&#x503C;&#x5668;&#x7684;&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5BF9;&#x4E00;&#x4E2A;&#x53EA;&#x6709;&#x53D6;&#x503C;&#x5668;&#xFF08;getter&#xFF09;&#x3001;&#x6CA1;&#x6709;&#x5B58;&#x503C;&#x5668;&#xFF08;setter&#xFF09;&#x7684;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> obj = {
  get v() { <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>; }
};
obj.v = <span class="hljs-number">2</span>;
<span class="hljs-comment">// Uncaught TypeError: Cannot set property v of #&lt;Object&gt; which has only a getter</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.v</code>&#x53EA;&#x6709;&#x53D6;&#x503C;&#x5668;&#xFF0C;&#x6CA1;&#x6709;&#x5B58;&#x503C;&#x5668;&#xFF0C;&#x5BF9;&#x5B83;&#x8FDB;&#x884C;&#x8D4B;&#x503C;&#x5C31;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<h3 id="&#x7981;&#x6B62;&#x6269;&#x5C55;&#x7684;&#x5BF9;&#x8C61;&#x4E0D;&#x53EF;&#x6269;&#x5C55;">&#x7981;&#x6B62;&#x6269;&#x5C55;&#x7684;&#x5BF9;&#x8C61;&#x4E0D;&#x53EF;&#x6269;&#x5C55;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5BF9;&#x7981;&#x6B62;&#x6269;&#x5C55;&#x7684;&#x5BF9;&#x8C61;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> obj = {};
<span class="hljs-built_in">Object</span>.preventExtensions(obj);
obj.v = <span class="hljs-number">1</span>;
<span class="hljs-comment">// Uncaught TypeError: Cannot add property v, object is not extensible</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj</code>&#x5BF9;&#x8C61;&#x7981;&#x6B62;&#x6269;&#x5C55;&#xFF0C;&#x6DFB;&#x52A0;&#x5C5E;&#x6027;&#x5C31;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<h3 id="eval&#x3001;arguments-&#x4E0D;&#x53EF;&#x7528;&#x4F5C;&#x6807;&#x8BC6;&#x540D;">eval&#x3001;arguments &#x4E0D;&#x53EF;&#x7528;&#x4F5C;&#x6807;&#x8BC6;&#x540D;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x4F7F;&#x7528;<code>eval</code>&#x6216;&#x8005;<code>arguments</code>&#x4F5C;&#x4E3A;&#x6807;&#x8BC6;&#x540D;&#xFF0C;&#x5C06;&#x4F1A;&#x62A5;&#x9519;&#x3002;&#x4E0B;&#x9762;&#x7684;&#x8BED;&#x53E5;&#x90FD;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> <span class="hljs-built_in">eval</span> = <span class="hljs-number">17</span>;
<span class="hljs-keyword">var</span> <span class="hljs-built_in">arguments</span> = <span class="hljs-number">17</span>;
<span class="hljs-keyword">var</span> obj = { set p(<span class="hljs-built_in">arguments</span>) { } };
<span class="hljs-keyword">try</span> { } <span class="hljs-keyword">catch</span> (<span class="hljs-built_in">arguments</span>) { }
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">x</span>(<span class="hljs-params">eval</span>) </span>{ }
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">arguments</span>(<span class="hljs-params"></span>) </span>{ }
<span class="hljs-keyword">var</span> y = <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">eval</span>(<span class="hljs-params"></span>) </span>{ };
<span class="hljs-keyword">var</span> f = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Function</span>(<span class="hljs-string">&apos;arguments&apos;</span>, <span class="hljs-string">&quot;&apos;use strict&apos;; return 17;&quot;</span>);
<span class="hljs-comment">// SyntaxError: Unexpected eval or arguments in strict mode</span>
</code></pre>
<h3 id="&#x51FD;&#x6570;&#x4E0D;&#x80FD;&#x6709;&#x91CD;&#x540D;&#x7684;&#x53C2;&#x6570;">&#x51FD;&#x6570;&#x4E0D;&#x80FD;&#x6709;&#x91CD;&#x540D;&#x7684;&#x53C2;&#x6570;</h3>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5982;&#x679C;&#x51FD;&#x6570;&#x6709;&#x591A;&#x4E2A;&#x91CD;&#x540D;&#x7684;&#x53C2;&#x6570;&#xFF0C;&#x53EF;&#x4EE5;&#x7528;<code>arguments[i]</code>&#x8BFB;&#x53D6;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x8FD9;&#x5C5E;&#x4E8E;&#x8BED;&#x6CD5;&#x9519;&#x8BEF;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params">a, a, b</span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">return</span> a + b;
}
<span class="hljs-comment">// Uncaught SyntaxError: Duplicate parameter name not allowed in this context</span>
</code></pre>
<h3 id="&#x7981;&#x6B62;&#x516B;&#x8FDB;&#x5236;&#x7684;&#x524D;&#x7F00;0&#x8868;&#x793A;&#x6CD5;">&#x7981;&#x6B62;&#x516B;&#x8FDB;&#x5236;&#x7684;&#x524D;&#x7F00;0&#x8868;&#x793A;&#x6CD5;</h3>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x6574;&#x6570;&#x7684;&#x7B2C;&#x4E00;&#x4F4D;&#x5982;&#x679C;&#x662F;<code>0</code>&#xFF0C;&#x8868;&#x793A;&#x8FD9;&#x662F;&#x516B;&#x8FDB;&#x5236;&#x6570;&#xFF0C;&#x6BD4;&#x5982;<code>0100</code>&#x7B49;&#x4E8E;&#x5341;&#x8FDB;&#x5236;&#x7684;64&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7981;&#x6B62;&#x8FD9;&#x79CD;&#x8868;&#x793A;&#x6CD5;&#xFF0C;&#x6574;&#x6570;&#x7B2C;&#x4E00;&#x4F4D;&#x4E3A;<code>0</code>&#xFF0C;&#x5C06;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> n = <span class="hljs-number">0100</span>;
<span class="hljs-comment">// Uncaught SyntaxError: Octal literals are not allowed in strict mode.</span>
</code></pre>
<h2 id="&#x589E;&#x5F3A;&#x7684;&#x5B89;&#x5168;&#x63AA;&#x65BD;">&#x589E;&#x5F3A;&#x7684;&#x5B89;&#x5168;&#x63AA;&#x65BD;</h2>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x589E;&#x5F3A;&#x4E86;&#x5B89;&#x5168;&#x4FDD;&#x62A4;&#xFF0C;&#x4ECE;&#x8BED;&#x6CD5;&#x4E0A;&#x9632;&#x6B62;&#x4E86;&#x4E00;&#x4E9B;&#x4E0D;&#x5C0F;&#x5FC3;&#x4F1A;&#x51FA;&#x73B0;&#x7684;&#x9519;&#x8BEF;&#x3002;</p>
<h3 id="&#x5168;&#x5C40;&#x53D8;&#x91CF;&#x663E;&#x5F0F;&#x58F0;&#x660E;">&#x5168;&#x5C40;&#x53D8;&#x91CF;&#x663E;&#x5F0F;&#x58F0;&#x660E;</h3>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E2D;&#xFF0C;&#x5982;&#x679C;&#x4E00;&#x4E2A;&#x53D8;&#x91CF;&#x6CA1;&#x6709;&#x58F0;&#x660E;&#x5C31;&#x8D4B;&#x503C;&#xFF0C;&#x9ED8;&#x8BA4;&#x662F;&#x5168;&#x5C40;&#x53D8;&#x91CF;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7981;&#x6B62;&#x8FD9;&#x79CD;&#x7528;&#x6CD5;&#xFF0C;&#x5168;&#x5C40;&#x53D8;&#x91CF;&#x5FC5;&#x987B;&#x663E;&#x5F0F;&#x58F0;&#x660E;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;

v = <span class="hljs-number">1</span>; <span class="hljs-comment">// &#x62A5;&#x9519;&#xFF0C;v&#x672A;&#x58F0;&#x660E;</span>

<span class="hljs-keyword">for</span> (i = <span class="hljs-number">0</span>; i &lt; <span class="hljs-number">2</span>; i++) { <span class="hljs-comment">// &#x62A5;&#x9519;&#xFF0C;i &#x672A;&#x58F0;&#x660E;</span>
  <span class="hljs-comment">// ...</span>
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params"></span>) </span>{
  x = <span class="hljs-number">123</span>;
}
f() <span class="hljs-comment">// &#x62A5;&#x9519;&#xFF0C;&#x672A;&#x58F0;&#x660E;&#x5C31;&#x521B;&#x5EFA;&#x4E00;&#x4E2A;&#x5168;&#x5C40;&#x53D8;&#x91CF;</span>
</code></pre>
<p>&#x56E0;&#x6B64;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x53D8;&#x91CF;&#x90FD;&#x5FC5;&#x987B;&#x5148;&#x58F0;&#x660E;&#xFF0C;&#x7136;&#x540E;&#x518D;&#x4F7F;&#x7528;&#x3002;</p>
<h3 id="&#x7981;&#x6B62;-this-&#x5173;&#x952E;&#x5B57;&#x6307;&#x5411;&#x5168;&#x5C40;&#x5BF9;&#x8C61;">&#x7981;&#x6B62; this &#x5173;&#x952E;&#x5B57;&#x6307;&#x5411;&#x5168;&#x5C40;&#x5BF9;&#x8C61;</h3>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x51FD;&#x6570;&#x5185;&#x90E8;&#x7684;<code>this</code>&#x53EF;&#x80FD;&#x4F1A;&#x6307;&#x5411;&#x5168;&#x5C40;&#x5BF9;&#x8C61;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7981;&#x6B62;&#x8FD9;&#x79CD;&#x7528;&#x6CD5;&#xFF0C;&#x907F;&#x514D;&#x65E0;&#x610F;&#x95F4;&#x521B;&#x9020;&#x5168;&#x5C40;&#x53D8;&#x91CF;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// &#x6B63;&#x5E38;&#x6A21;&#x5F0F;</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-built_in">console</span>.log(<span class="hljs-keyword">this</span> === <span class="hljs-built_in">window</span>);
}
f() <span class="hljs-comment">// true</span>

<span class="hljs-comment">// &#x4E25;&#x683C;&#x6A21;&#x5F0F;</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-built_in">console</span>.log(<span class="hljs-keyword">this</span> === <span class="hljs-literal">undefined</span>);
}
f() <span class="hljs-comment">// true</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x7684;&#x51FD;&#x6570;&#x4F53;&#x5185;&#x90E8;<code>this</code>&#x662F;<code>undefined</code>&#x3002;</p>
<p>&#x8FD9;&#x79CD;&#x9650;&#x5236;&#x5BF9;&#x4E8E;&#x6784;&#x9020;&#x51FD;&#x6570;&#x5C24;&#x5176;&#x6709;&#x7528;&#x3002;&#x4F7F;&#x7528;&#x6784;&#x9020;&#x51FD;&#x6570;&#x65F6;&#xFF0C;&#x6709;&#x65F6;&#x5FD8;&#x4E86;&#x52A0;<code>new</code>&#xFF0C;&#x8FD9;&#x65F6;<code>this</code>&#x4E0D;&#x518D;&#x6307;&#x5411;&#x5168;&#x5C40;&#x5BF9;&#x8C61;&#xFF0C;&#x800C;&#x662F;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">this</span>.a = <span class="hljs-number">1</span>;
};

f();<span class="hljs-comment">// &#x62A5;&#x9519;&#xFF0C;this &#x672A;&#x5B9A;&#x4E49;</span>
</code></pre>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x51FD;&#x6570;&#x76F4;&#x63A5;&#x8C03;&#x7528;&#x65F6;&#xFF08;&#x4E0D;&#x4F7F;&#x7528;<code>new</code>&#x8C03;&#x7528;&#xFF09;&#xFF0C;&#x51FD;&#x6570;&#x5185;&#x90E8;&#x7684;<code>this</code>&#x8868;&#x793A;<code>undefined</code>&#xFF08;&#x672A;&#x5B9A;&#x4E49;&#xFF09;&#xFF0C;&#x56E0;&#x6B64;&#x53EF;&#x4EE5;&#x7528;<code>call</code>&#x3001;<code>apply</code>&#x548C;<code>bind</code>&#x65B9;&#x6CD5;&#xFF0C;&#x5C06;&#x4EFB;&#x610F;&#x503C;&#x7ED1;&#x5B9A;&#x5728;<code>this</code>&#x4E0A;&#x9762;&#x3002;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;<code>this</code>&#x6307;&#x5411;&#x5168;&#x5C40;&#x5BF9;&#x8C61;&#xFF0C;&#x5982;&#x679C;&#x7ED1;&#x5B9A;&#x7684;&#x503C;&#x662F;&#x975E;&#x5BF9;&#x8C61;&#xFF0C;&#x5C06;&#x88AB;&#x81EA;&#x52A8;&#x8F6C;&#x4E3A;&#x5BF9;&#x8C61;&#x518D;&#x7ED1;&#x5B9A;&#x4E0A;&#x53BB;&#xFF0C;&#x800C;<code>null</code>&#x548C;<code>undefined</code>&#x8FD9;&#x4E24;&#x4E2A;&#x65E0;&#x6CD5;&#x8F6C;&#x6210;&#x5BF9;&#x8C61;&#x7684;&#x503C;&#xFF0C;&#x5C06;&#x88AB;&#x5FFD;&#x7565;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// &#x6B63;&#x5E38;&#x6A21;&#x5F0F;</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">fun</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>;
}

fun() <span class="hljs-comment">// window</span>
fun.call(<span class="hljs-number">2</span>) <span class="hljs-comment">// Number {2}</span>
fun.call(<span class="hljs-literal">true</span>) <span class="hljs-comment">// Boolean {true}</span>
fun.call(<span class="hljs-literal">null</span>) <span class="hljs-comment">// window</span>
fun.call(<span class="hljs-literal">undefined</span>) <span class="hljs-comment">// window</span>

<span class="hljs-comment">// &#x4E25;&#x683C;&#x6A21;&#x5F0F;</span>
<span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">fun</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>;
}

fun() <span class="hljs-comment">//undefined</span>
fun.call(<span class="hljs-number">2</span>) <span class="hljs-comment">// 2</span>
fun.call(<span class="hljs-literal">true</span>) <span class="hljs-comment">// true</span>
fun.call(<span class="hljs-literal">null</span>) <span class="hljs-comment">// null</span>
fun.call(<span class="hljs-literal">undefined</span>) <span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x53EF;&#x4EE5;&#x628A;&#x4EFB;&#x610F;&#x7C7B;&#x578B;&#x7684;&#x503C;&#xFF0C;&#x7ED1;&#x5B9A;&#x5728;<code>this</code>&#x4E0A;&#x9762;&#x3002;</p>
<h3 id="&#x7981;&#x6B62;&#x4F7F;&#x7528;-fncallee&#x3001;fncaller">&#x7981;&#x6B62;&#x4F7F;&#x7528; fn.callee&#x3001;fn.caller</h3>
<p>&#x51FD;&#x6570;&#x5185;&#x90E8;&#x4E0D;&#x5F97;&#x4F7F;&#x7528;<code>fn.caller</code>&#x3001;<code>fn.arguments</code>&#xFF0C;&#x5426;&#x5219;&#x4F1A;&#x62A5;&#x9519;&#x3002;&#x8FD9;&#x610F;&#x5473;&#x7740;&#x4E0D;&#x80FD;&#x5728;&#x51FD;&#x6570;&#x5185;&#x90E8;&#x5F97;&#x5230;&#x8C03;&#x7528;&#x6808;&#x4E86;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f1</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  f1.caller;    <span class="hljs-comment">// &#x62A5;&#x9519;</span>
  f1.arguments; <span class="hljs-comment">// &#x62A5;&#x9519;</span>
}

f1();
</code></pre>
<h3 id="&#x7981;&#x6B62;&#x4F7F;&#x7528;-argumentscallee&#x3001;argumentscaller">&#x7981;&#x6B62;&#x4F7F;&#x7528; arguments.callee&#x3001;arguments.caller</h3>
<p><code>arguments.callee</code>&#x548C;<code>arguments.caller</code>&#x662F;&#x4E24;&#x4E2A;&#x5386;&#x53F2;&#x9057;&#x7559;&#x7684;&#x53D8;&#x91CF;&#xFF0C;&#x4ECE;&#x6765;&#x6CA1;&#x6709;&#x6807;&#x51C6;&#x5316;&#x8FC7;&#xFF0C;&#x73B0;&#x5728;&#x5DF2;&#x7ECF;&#x53D6;&#x6D88;&#x4E86;&#x3002;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#x8C03;&#x7528;&#x5B83;&#x4EEC;&#x6CA1;&#x6709;&#x4EC0;&#x4E48;&#x4F5C;&#x7528;&#xFF0C;&#x4F46;&#x662F;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x660E;&#x786E;&#x89C4;&#x5B9A;&#xFF0C;&#x51FD;&#x6570;&#x5185;&#x90E8;&#x4F7F;&#x7528;<code>arguments.callee</code>&#x3001;<code>arguments.caller</code>&#x5C06;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> f = <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-built_in">arguments</span>.callee;
};

f(); <span class="hljs-comment">// &#x62A5;&#x9519;</span>
</code></pre>
<h3 id="&#x7981;&#x6B62;&#x5220;&#x9664;&#x53D8;&#x91CF;">&#x7981;&#x6B62;&#x5220;&#x9664;&#x53D8;&#x91CF;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#x65E0;&#x6CD5;&#x5220;&#x9664;&#x53D8;&#x91CF;&#xFF0C;&#x5982;&#x679C;&#x4F7F;&#x7528;<code>delete</code>&#x547D;&#x4EE4;&#x5220;&#x9664;&#x4E00;&#x4E2A;&#x53D8;&#x91CF;&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;&#x53EA;&#x6709;&#x5BF9;&#x8C61;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x4E14;&#x5C5E;&#x6027;&#x7684;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>configurable</code>&#x5C5E;&#x6027;&#x8BBE;&#x7F6E;&#x4E3A;<code>true</code>&#xFF0C;&#x624D;&#x80FD;&#x88AB;<code>delete</code>&#x547D;&#x4EE4;&#x5220;&#x9664;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> x;
<span class="hljs-keyword">delete</span> x; <span class="hljs-comment">// &#x8BED;&#x6CD5;&#x9519;&#x8BEF;</span>

<span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.create(<span class="hljs-literal">null</span>, {
  x: {
    value: <span class="hljs-number">1</span>,
    configurable: <span class="hljs-literal">true</span>
  }
});
<span class="hljs-keyword">delete</span> obj.x; <span class="hljs-comment">// &#x5220;&#x9664;&#x6210;&#x529F;</span>
</code></pre>
<h2 id="&#x9759;&#x6001;&#x7ED1;&#x5B9A;">&#x9759;&#x6001;&#x7ED1;&#x5B9A;</h2>
<p>JavaScript &#x8BED;&#x8A00;&#x7684;&#x4E00;&#x4E2A;&#x7279;&#x70B9;&#xFF0C;&#x5C31;&#x662F;&#x5141;&#x8BB8;&#x201C;&#x52A8;&#x6001;&#x7ED1;&#x5B9A;&#x201D;&#xFF0C;&#x5373;&#x67D0;&#x4E9B;&#x5C5E;&#x6027;&#x548C;&#x65B9;&#x6CD5;&#x5230;&#x5E95;&#x5C5E;&#x4E8E;&#x54EA;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x4E0D;&#x662F;&#x5728;&#x7F16;&#x8BD1;&#x65F6;&#x786E;&#x5B9A;&#x7684;&#xFF0C;&#x800C;&#x662F;&#x5728;&#x8FD0;&#x884C;&#x65F6;&#xFF08;runtime&#xFF09;&#x786E;&#x5B9A;&#x7684;&#x3002;</p>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x5BF9;&#x52A8;&#x6001;&#x7ED1;&#x5B9A;&#x505A;&#x4E86;&#x4E00;&#x4E9B;&#x9650;&#x5236;&#x3002;&#x67D0;&#x4E9B;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x53EA;&#x5141;&#x8BB8;&#x9759;&#x6001;&#x7ED1;&#x5B9A;&#x3002;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;&#x5C5E;&#x6027;&#x548C;&#x65B9;&#x6CD5;&#x5230;&#x5E95;&#x5F52;&#x5C5E;&#x54EA;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x5FC5;&#x987B;&#x5728;&#x7F16;&#x8BD1;&#x9636;&#x6BB5;&#x5C31;&#x786E;&#x5B9A;&#x3002;&#x8FD9;&#x6837;&#x505A;&#x6709;&#x5229;&#x4E8E;&#x7F16;&#x8BD1;&#x6548;&#x7387;&#x7684;&#x63D0;&#x9AD8;&#xFF0C;&#x4E5F;&#x4F7F;&#x5F97;&#x4EE3;&#x7801;&#x66F4;&#x5BB9;&#x6613;&#x9605;&#x8BFB;&#xFF0C;&#x66F4;&#x5C11;&#x51FA;&#x73B0;&#x610F;&#x5916;&#x3002;</p>
<p>&#x5177;&#x4F53;&#x6765;&#x8BF4;&#xFF0C;&#x6D89;&#x53CA;&#x4EE5;&#x4E0B;&#x51E0;&#x4E2A;&#x65B9;&#x9762;&#x3002;</p>
<h3 id="&#x7981;&#x6B62;&#x4F7F;&#x7528;-with-&#x8BED;&#x53E5;">&#x7981;&#x6B62;&#x4F7F;&#x7528; with &#x8BED;&#x53E5;</h3>
<p>&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x4F7F;&#x7528;<code>with</code>&#x8BED;&#x53E5;&#x5C06;&#x62A5;&#x9519;&#x3002;&#x56E0;&#x4E3A;<code>with</code>&#x8BED;&#x53E5;&#x65E0;&#x6CD5;&#x5728;&#x7F16;&#x8BD1;&#x65F6;&#x5C31;&#x786E;&#x5B9A;&#xFF0C;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x5230;&#x5E95;&#x5F52;&#x5C5E;&#x54EA;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x4ECE;&#x800C;&#x5F71;&#x54CD;&#x4E86;&#x7F16;&#x8BD1;&#x6548;&#x679C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> v  = <span class="hljs-number">1</span>;
<span class="hljs-keyword">var</span> obj = {};

<span class="hljs-keyword">with</span> (obj) {
  v = <span class="hljs-number">2</span>;
}
<span class="hljs-comment">// Uncaught SyntaxError: Strict mode code may not include a with statement</span>
</code></pre>
<h3 id="&#x521B;&#x8BBE;-eval-&#x4F5C;&#x7528;&#x57DF;">&#x521B;&#x8BBE; eval &#x4F5C;&#x7528;&#x57DF;</h3>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;JavaScript &#x8BED;&#x8A00;&#x6709;&#x4E24;&#x79CD;&#x53D8;&#x91CF;&#x4F5C;&#x7528;&#x57DF;&#xFF08;scope&#xFF09;&#xFF1A;&#x5168;&#x5C40;&#x4F5C;&#x7528;&#x57DF;&#x548C;&#x51FD;&#x6570;&#x4F5C;&#x7528;&#x57DF;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x521B;&#x8BBE;&#x4E86;&#x7B2C;&#x4E09;&#x79CD;&#x4F5C;&#x7528;&#x57DF;&#xFF1A;<code>eval</code>&#x4F5C;&#x7528;&#x57DF;&#x3002;</p>
<p>&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;<code>eval</code>&#x8BED;&#x53E5;&#x7684;&#x4F5C;&#x7528;&#x57DF;&#xFF0C;&#x53D6;&#x51B3;&#x4E8E;&#x5B83;&#x5904;&#x4E8E;&#x5168;&#x5C40;&#x4F5C;&#x7528;&#x57DF;&#xFF0C;&#x8FD8;&#x662F;&#x51FD;&#x6570;&#x4F5C;&#x7528;&#x57DF;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;<code>eval</code>&#x8BED;&#x53E5;&#x672C;&#x8EAB;&#x5C31;&#x662F;&#x4E00;&#x4E2A;&#x4F5C;&#x7528;&#x57DF;&#xFF0C;&#x4E0D;&#x518D;&#x80FD;&#x591F;&#x5728;&#x5176;&#x6240;&#x8FD0;&#x884C;&#x7684;&#x4F5C;&#x7528;&#x57DF;&#x521B;&#x8BBE;&#x65B0;&#x7684;&#x53D8;&#x91CF;&#x4E86;&#xFF0C;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;<code>eval</code>&#x6240;&#x751F;&#x6210;&#x7684;&#x53D8;&#x91CF;&#x53EA;&#x80FD;&#x7528;&#x4E8E;<code>eval</code>&#x5185;&#x90E8;&#x3002;</p>
<pre><code class="lang-javascript">(<span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">var</span> x = <span class="hljs-number">2</span>;
  <span class="hljs-built_in">console</span>.log(<span class="hljs-built_in">eval</span>(<span class="hljs-string">&apos;var x = 5; x&apos;</span>)) <span class="hljs-comment">// 5</span>
  <span class="hljs-built_in">console</span>.log(x) <span class="hljs-comment">// 2</span>
})()
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x7531;&#x4E8E;<code>eval</code>&#x8BED;&#x53E5;&#x5185;&#x90E8;&#x662F;&#x4E00;&#x4E2A;&#x72EC;&#x7ACB;&#x4F5C;&#x7528;&#x57DF;&#xFF0C;&#x6240;&#x4EE5;&#x5185;&#x90E8;&#x7684;&#x53D8;&#x91CF;<code>x</code>&#x4E0D;&#x4F1A;&#x6CC4;&#x9732;&#x5230;&#x5916;&#x90E8;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x5982;&#x679C;&#x5E0C;&#x671B;<code>eval</code>&#x8BED;&#x53E5;&#x4E5F;&#x4F7F;&#x7528;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x6709;&#x4E24;&#x79CD;&#x65B9;&#x5F0F;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// &#x65B9;&#x5F0F;&#x4E00;</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f1</span>(<span class="hljs-params">str</span>)</span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">return</span> <span class="hljs-built_in">eval</span>(str);
}
f1(<span class="hljs-string">&apos;undeclared_variable = 1&apos;</span>); <span class="hljs-comment">// &#x62A5;&#x9519;</span>

<span class="hljs-comment">// &#x65B9;&#x5F0F;&#x4E8C;</span>
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f2</span>(<span class="hljs-params">str</span>)</span>{
  <span class="hljs-keyword">return</span> <span class="hljs-built_in">eval</span>(str);
}
f2(<span class="hljs-string">&apos;&quot;use strict&quot;;undeclared_variable = 1&apos;</span>)  <span class="hljs-comment">// &#x62A5;&#x9519;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4E24;&#x79CD;&#x5199;&#x6CD5;&#xFF0C;<code>eval</code>&#x5185;&#x90E8;&#x4F7F;&#x7528;&#x7684;&#x90FD;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x3002;</p>
<h3 id="arguments-&#x4E0D;&#x518D;&#x8FFD;&#x8E2A;&#x53C2;&#x6570;&#x7684;&#x53D8;&#x5316;">arguments &#x4E0D;&#x518D;&#x8FFD;&#x8E2A;&#x53C2;&#x6570;&#x7684;&#x53D8;&#x5316;</h3>
<p>&#x53D8;&#x91CF;<code>arguments</code>&#x4EE3;&#x8868;&#x51FD;&#x6570;&#x7684;&#x53C2;&#x6570;&#x3002;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x51FD;&#x6570;&#x5185;&#x90E8;&#x6539;&#x53D8;&#x53C2;&#x6570;&#x4E0E;<code>arguments</code>&#x7684;&#x8054;&#x7CFB;&#x88AB;&#x5207;&#x65AD;&#x4E86;&#xFF0C;&#x4E24;&#x8005;&#x4E0D;&#x518D;&#x5B58;&#x5728;&#x8054;&#x52A8;&#x5173;&#x7CFB;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params">a</span>) </span>{
  a = <span class="hljs-number">2</span>;
  <span class="hljs-keyword">return</span> [a, <span class="hljs-built_in">arguments</span>[<span class="hljs-number">0</span>]];
}
f(<span class="hljs-number">1</span>); <span class="hljs-comment">// &#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E3A;[2, 2]</span>

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f</span>(<span class="hljs-params">a</span>) </span>{
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  a = <span class="hljs-number">2</span>;
  <span class="hljs-keyword">return</span> [a, <span class="hljs-built_in">arguments</span>[<span class="hljs-number">0</span>]];
}
f(<span class="hljs-number">1</span>); <span class="hljs-comment">// &#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E3A;[2, 1]</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x6539;&#x53D8;&#x51FD;&#x6570;&#x7684;&#x53C2;&#x6570;&#xFF0C;&#x4E0D;&#x4F1A;&#x53CD;&#x5E94;&#x5230;<code>arguments</code>&#x5BF9;&#x8C61;&#x4E0A;&#x6765;&#x3002;</p>
<h2 id="&#x5411;&#x4E0B;&#x4E00;&#x4E2A;&#x7248;&#x672C;&#x7684;-javascript-&#x8FC7;&#x6E21;">&#x5411;&#x4E0B;&#x4E00;&#x4E2A;&#x7248;&#x672C;&#x7684; JavaScript &#x8FC7;&#x6E21;</h2>
<p>JavaScript &#x8BED;&#x8A00;&#x7684;&#x4E0B;&#x4E00;&#x4E2A;&#x7248;&#x672C;&#x662F; ECMAScript 6&#xFF0C;&#x4E3A;&#x4E86;&#x5E73;&#x7A33;&#x8FC7;&#x6E21;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x5F15;&#x5165;&#x4E86;&#x4E00;&#x4E9B; ES6 &#x8BED;&#x6CD5;&#x3002;</p>
<h3 id="&#x975E;&#x51FD;&#x6570;&#x4EE3;&#x7801;&#x5757;&#x4E0D;&#x5F97;&#x58F0;&#x660E;&#x51FD;&#x6570;">&#x975E;&#x51FD;&#x6570;&#x4EE3;&#x7801;&#x5757;&#x4E0D;&#x5F97;&#x58F0;&#x660E;&#x51FD;&#x6570;</h3>
<p>ES6 &#x4F1A;&#x5F15;&#x5165;&#x5757;&#x7EA7;&#x4F5C;&#x7528;&#x57DF;&#x3002;&#x4E3A;&#x4E86;&#x4E0E;&#x65B0;&#x7248;&#x672C;&#x63A5;&#x8F68;&#xFF0C;ES5 &#x7684;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x53EA;&#x5141;&#x8BB8;&#x5728;&#x5168;&#x5C40;&#x4F5C;&#x7528;&#x57DF;&#x6216;&#x51FD;&#x6570;&#x4F5C;&#x7528;&#x57DF;&#x58F0;&#x660E;&#x51FD;&#x6570;&#x3002;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;&#x4E0D;&#x5141;&#x8BB8;&#x5728;&#x975E;&#x51FD;&#x6570;&#x7684;&#x4EE3;&#x7801;&#x5757;&#x5185;&#x58F0;&#x660E;&#x51FD;&#x6570;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">if</span> (<span class="hljs-literal">true</span>) {
  <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f1</span>(<span class="hljs-params"></span>) </span>{ } <span class="hljs-comment">// &#x8BED;&#x6CD5;&#x9519;&#x8BEF;</span>
}

<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; <span class="hljs-number">5</span>; i++) {
  <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">f2</span>(<span class="hljs-params"></span>) </span>{ } <span class="hljs-comment">// &#x8BED;&#x6CD5;&#x9519;&#x8BEF;</span>
}
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x5728;<code>if</code>&#x4EE3;&#x7801;&#x5757;&#x548C;<code>for</code>&#x4EE3;&#x7801;&#x5757;&#x4E2D;&#x58F0;&#x660E;&#x4E86;&#x51FD;&#x6570;&#xFF0C;ES5 &#x73AF;&#x5883;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x5982;&#x679C;&#x662F; ES6 &#x73AF;&#x5883;&#xFF0C;&#x4E0A;&#x9762;&#x7684;&#x4EE3;&#x7801;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#xFF0C;&#x56E0;&#x4E3A; ES6 &#x5141;&#x8BB8;&#x5728;&#x4EE3;&#x7801;&#x5757;&#x4E4B;&#x4E2D;&#x58F0;&#x660E;&#x51FD;&#x6570;&#x3002;</p>
<h3 id="&#x4FDD;&#x7559;&#x5B57;">&#x4FDD;&#x7559;&#x5B57;</h3>
<p>&#x4E3A;&#x4E86;&#x5411;&#x5C06;&#x6765; JavaScript &#x7684;&#x65B0;&#x7248;&#x672C;&#x8FC7;&#x6E21;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x65B0;&#x589E;&#x4E86;&#x4E00;&#x4E9B;&#x4FDD;&#x7559;&#x5B57;&#xFF08;implements&#x3001;interface&#x3001;let&#x3001;package&#x3001;private&#x3001;protected&#x3001;public&#x3001;static&#x3001;yield&#x7B49;&#xFF09;&#x3002;&#x4F7F;&#x7528;&#x8FD9;&#x4E9B;&#x8BCD;&#x4F5C;&#x4E3A;&#x53D8;&#x91CF;&#x540D;&#x5C06;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">package</span>(<span class="hljs-params">protected</span>) </span>{ <span class="hljs-comment">// &#x8BED;&#x6CD5;&#x9519;&#x8BEF;</span>
<span class="hljs-meta">  &apos;use strict&apos;</span>;
  <span class="hljs-keyword">var</span> implements; <span class="hljs-comment">// &#x8BED;&#x6CD5;&#x9519;&#x8BEF;</span>
}
</code></pre>
<h2 id="&#x53C2;&#x8003;&#x94FE;&#x63A5;">&#x53C2;&#x8003;&#x94FE;&#x63A5;</h2>
<ul>
<li>MDN, <a href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Functions_and_function_scope/Strict_mode" target="_blank" rel="nofollow">Strict mode</a></li>
<li>Dr. Axel Rauschmayer, <a href="http://www.2ality.com/2011/10/strict-mode-hatred.html" target="_blank" rel="nofollow">JavaScript: Why the hatred for strict mode?</a></li>
<li>Dr. Axel Rauschmayer&#xFF0C;<a href="http://www.2ality.com/2011/01/javascripts-strict-mode-summary.html" target="_blank" rel="nofollow">JavaScript&#x2019;s strict mode: a summary</a></li>
<li>Douglas Crockford, <a href="http://www.yuiblog.com/blog/2010/12/14/strict-mode-is-coming-to-town/" target="_blank" rel="nofollow">Strict Mode Is Coming To Town</a></li>
<li><a href="http://java-script.limewebs.com/strictMode/test_hosted.html" target="_blank" rel="nofollow">JavaScript Strict Mode Support</a></li>
</ul>




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